1. Field of the Invention
The present invention relates to a compact motor with a speed reducing mechanism and, more particularly, to such a compact motor having a function of oscillating a low-speed output shaft.
2. Description of the Related Art
A louver of an air conditioner, for example, is periodically oscillated to change a blowing direction of cool air or the like generated in the air conditioner, thereby uniformly circulate the cool air in a room.
FIG. 20 shows a drive mechanism for such a louver of an air conditioner in the related art.
As shown in FIG. 20, three louvers 71, 72, and 73 are rotatably supported at their lower and upper shaft portions 74 and 75 through bearings 78 to lower and upper boards 76 and 77. Lever pins 79 are formed on the louvers 71, 72, and 73. The lever pins 79 are rotatably inserted in holes 91 formed through an oscillating lever 90.
The oscillating lever 90 is supported by a guide (not shown) so as to be linearly reciprocatable in a direction of double-headed arrow F. The oscillating lever 90 is provided with a driven hole 92. A crank 93 bent eccentrically from an output shaft 100a of a compact motor 100 with a speed reducing mechanism is inserted in the driven hole 92 of the oscillating lever 90.
The oscillating operation of the louvers of the air conditioner mentioned above will be described.
The output shaft 100a of the compact motor 100 is rotated at a low speed, and the crank 93 formed at the end of the output shaft 100a is rotated so as to draw a large circle as shown by an arrow P in FIG. 20.
The driven hole 92 of the oscillating lever 90 is elongated in a direction perpendicular to the direction F, so that the rotation of the crank 93 is converted into reciprocation of the oscillating lever 90 in the direction F. The reciprocation of the oscillating lever 90 is converted into repeated oscillation of the louvers 71, 72, and 73 about the axes of the shaft portions 74 and 75 by the engagement of the lever pins 79 with the holes 91. Thus, the cool air generated in the air conditioner can be uniformly circulated in a room.
Incidentally, when an overload is applied to the louver, the intermediate transmission members are possibly broken because of a problem of strength or mechanism. Various means of preventing such breakage have conventionally been applied to the louver.
As a means of preventing such breakage due to the problem of mechanism, a torque limiter such as a friction clutch is applied.
The above-mentioned compact motor used to drive the louver of the air conditioner in the related art has the following problems.
(1) The oscillating mechanism for the louver of the air conditioner includes many parts to cause an increase in cost. Furthermore, the oscillating mechanism has a large size, which cannot meet the requirement of reduction in size of the air conditioner.
The cool air generated in the air conditioner blows directly against the louver and the oscillating mechanism to generate dew on the louver and the oscillating mechanism. Accordingly, the drops of dew cause deterioration in insulating performance of electrical parts located under the louver and the oscillating mechanism and also cause the generation of rust.
Further, since the cool air blows against the oscillating mechanism, the flow of the cool air is disturbed by the oscillating mechanism. That is, the flow of the cool air cannot be supplied as a regular flow, thus reducing the performance of the air conditioner.
(2) The friction clutch has a disc plate connected to the low-speed output shaft and a friction plate adapted to slide on the disc plate, thereby preventing an overload applied to the low-speed output shaft from being transmitted to a reduction gear train in the compact motor. When the overload applied to the output shaft is removed, the sliding of the friction plate is stopped. However, the rotational positional relationship between the output shaft and the friction plate slips at this time from the original positional relationship prior to operation of the friction clutch. Accordingly, when the output shaft is restarted to rotate, an operational position of the louver is changed, which becomes a serious problem because an accurate oscillatory angle of the louver must be maintained in the air conditioner.